This invention generally relates to novel ferrosiloxanes compounds and their use as heat stabilizers for diorganopolysiloxanes. More particularily, the invention relates to those ferrosiloxane compounds made from iron carboxylates and N,N-disubstituted silylamine.
It is well recognized in the art that diorganopolysiloxanes are susceptible to breakdown through dipolymerization and oxidation upon exposure to temperatures in excess of 300.degree. C. for prolonged periods of time. This dipolymerization and oxidation ultimately results in a gelling of the diorganopolysiloxane. Various methods of stabilization have been proposed in the prior art to solve this problem. In most instances, soluble or partially soluble forms of transition metal compounds have been directly added to the siloxane polymer to be stabilized without further treatment of the resulting mixture as seen, for example, by the proposed use of carboxylate salts of iron, cobalt, nickel and copper as antioxidants in U.S. Pat. No. 2,445,567. The use of other types of antioxidants has also been proposed, e.g., ferrocenyl-substituted siloxanes, as seen in Chemical Abstracts, 72, page 32,635 P (1970) and U.S. Pat. No. 3,679,660, and iron oxide as proposed by U.S. Pat. No. 3,352,781. Recently, U.S. Pat. No. 3,002,927 has taught the use of iron salts of carboxylic acid along with mechanical aeration at greatly elevated temperatures of the siloxane mixture prior to use. The most recent method to overcome this problem is found in U.S. Pat. No. 3,865,784 which proposes that a mixture of a diorganopolysiloxane compound and an iron carbonyl compound, heated to at least 120.degree. C. in the presence of oxygen, produces a stabilized iron-containing diorganopolysiloxane.
Recent art relying upon non-ferrous materials include U.S. Pat. No. 3,884,950 which proposes the use of a cerium salt of an organic carboxylic acid soluble in aromatic hydrocarbons. Finally, Japanese KoKai No. 79/32,563 proposes the use of the reaction product of siloxanes with cerium carboxylates to improve the heat stability of the siloxanes.
The increasing importance of thermally stable diorganosiloxanes warrants a continuing search for novel stabilizer that are at once commercially feasible and yet effective in their applicability to the task at hand. Other objects and advantages of this invention will become readily apparent from the detailed description and appended claims.